This book describes the relaxation dynamics of rubbery materials, with the objective of providing a molecular basis for many physical properties. As the term comprises any amorphous, flexible ...
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This book describes the relaxation dynamics of rubbery materials, with the objective of providing a molecular basis for many physical properties. As the term comprises any amorphous, flexible macromolecule above its glass-transition temperature, rubber includes a broad class of substances, with a richness of behavior rivaled by few materials. The focus is mainly on the phenomenology, emphasizing anomalies and aspects that are incompletely understood and thus productive avenues for future research. Rubber is especially interesting because it has unique properties. It can exist in a state of equilibrium, unlike glassy or semicrystalline plastics, thermosetting resins, fibers, etc. These polymers have path-dependent morphologies and process-specific properties, which frustrate scientific inquiry, notwithstanding their practical utility. Among all materials only rubber exhibits high elasticity—the ability to recover from very large deformations. This property underlies most applications of elastomers and gave rise to its own field of study. Despite these singular characteristics, rubber is arguably the prototype for relaxation in soft matter. By copolymerizing different monomers, an enormous variety of chemical structures are available that, along with the ease of avoiding crystallization, makes make rubber ideal for the study of the glass transition, a major unsolved problem in condensed-matter physics. In the glassy state or when vitrification is imminent, polymers cannot easily be distinguished from molecular liquids, and the correspondence of many phenomena makes distinctions between molecular and polymeric liquids artificial. Accordingly, the scope of this book is not limited to polymer science, with the discussion often extending to small-molecule compounds, including simple liquids and liquid crystals.Less

Viscoelastic Behavior of Rubbery Materials

C. Michael Roland

Published in print: 2011-06-30

This book describes the relaxation dynamics of rubbery materials, with the objective of providing a molecular basis for many physical properties. As the term comprises any amorphous, flexible macromolecule above its glass-transition temperature, rubber includes a broad class of substances, with a richness of behavior rivaled by few materials. The focus is mainly on the phenomenology, emphasizing anomalies and aspects that are incompletely understood and thus productive avenues for future research. Rubber is especially interesting because it has unique properties. It can exist in a state of equilibrium, unlike glassy or semicrystalline plastics, thermosetting resins, fibers, etc. These polymers have path-dependent morphologies and process-specific properties, which frustrate scientific inquiry, notwithstanding their practical utility. Among all materials only rubber exhibits high elasticity—the ability to recover from very large deformations. This property underlies most applications of elastomers and gave rise to its own field of study. Despite these singular characteristics, rubber is arguably the prototype for relaxation in soft matter. By copolymerizing different monomers, an enormous variety of chemical structures are available that, along with the ease of avoiding crystallization, makes make rubber ideal for the study of the glass transition, a major unsolved problem in condensed-matter physics. In the glassy state or when vitrification is imminent, polymers cannot easily be distinguished from molecular liquids, and the correspondence of many phenomena makes distinctions between molecular and polymeric liquids artificial. Accordingly, the scope of this book is not limited to polymer science, with the discussion often extending to small-molecule compounds, including simple liquids and liquid crystals.

This book presents a dynamic new approach to the physics of enzymes and DNA from the perspective of materials science. Unified around the concept of molecular deformability—how proteins and DNA ...
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This book presents a dynamic new approach to the physics of enzymes and DNA from the perspective of materials science. Unified around the concept of molecular deformability—how proteins and DNA stretch, fold, and change shape—the book describes the complex molecules of life from the innovative perspective of materials properties and dynamics, in contrast to structural or purely chemical approaches. It covers a wealth of topics, including nonlinear deformability of enzymes and DNA; the chemo-dynamic cycle of enzymes; supra-molecular constructions with internal stress; nano-rheology and viscoelasticity; and chemical kinetics, Brownian motion, and barrier crossing. Essential reading for researchers in materials science, engineering, and nanotechnology, the book also describes the landmark experiments that have established the materials properties and energy landscape of large biological molecules. The book gives graduate students a working knowledge of model building in statistical mechanics, making it an essential resource for tomorrow's experimentalists in this cutting-edge field. In addition, mathematical methods are introduced in the bio-molecular context. The result is a generalized approach to mathematical problem solving that enables students to apply their findings more broadly.Less

Molecular Machines : A Materials Science Approach

Giovanni Zocchi

Published in print: 2018-07-10

This book presents a dynamic new approach to the physics of enzymes and DNA from the perspective of materials science. Unified around the concept of molecular deformability—how proteins and DNA stretch, fold, and change shape—the book describes the complex molecules of life from the innovative perspective of materials properties and dynamics, in contrast to structural or purely chemical approaches. It covers a wealth of topics, including nonlinear deformability of enzymes and DNA; the chemo-dynamic cycle of enzymes; supra-molecular constructions with internal stress; nano-rheology and viscoelasticity; and chemical kinetics, Brownian motion, and barrier crossing. Essential reading for researchers in materials science, engineering, and nanotechnology, the book also describes the landmark experiments that have established the materials properties and energy landscape of large biological molecules. The book gives graduate students a working knowledge of model building in statistical mechanics, making it an essential resource for tomorrow's experimentalists in this cutting-edge field. In addition, mathematical methods are introduced in the bio-molecular context. The result is a generalized approach to mathematical problem solving that enables students to apply their findings more broadly.

This chapter discusses the deformability of enzymes. This property allows enzymes to couple a chemical process to a cycle of deformations of the molecule, which can perform a task in the cell. This ...
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This chapter discusses the deformability of enzymes. This property allows enzymes to couple a chemical process to a cycle of deformations of the molecule, which can perform a task in the cell. This is the celebrated “molecular machine” aspect of enzymes. The dynamics of enzyme deformability presents universal features when ensemble-averaged trajectories are examined. The mechanical response is viscoelastic. The remainder of the chapter covers the nonlinearity of the enzyme's mechanics, timescales, enzymatic cycle and viscoelasticity, internal dissipation, origin of the restoring force g, models based on chemical kinetics, different levels of microscopic description, connection to information flow, normal mode analysis, many states of the folded protein, and interesting topics in nonequilibrium thermodynamics relating to enzyme dynamics.Less

Dynamics of Enzyme Action

Giovanni Zocchi

Published in print: 2018-07-10

This chapter discusses the deformability of enzymes. This property allows enzymes to couple a chemical process to a cycle of deformations of the molecule, which can perform a task in the cell. This is the celebrated “molecular machine” aspect of enzymes. The dynamics of enzyme deformability presents universal features when ensemble-averaged trajectories are examined. The mechanical response is viscoelastic. The remainder of the chapter covers the nonlinearity of the enzyme's mechanics, timescales, enzymatic cycle and viscoelasticity, internal dissipation, origin of the restoring force g, models based on chemical kinetics, different levels of microscopic description, connection to information flow, normal mode analysis, many states of the folded protein, and interesting topics in nonequilibrium thermodynamics relating to enzyme dynamics.

We present a comprehensive overview of microrheology, emphasizing the underlying theory, practical aspects of its implementation, and current applications to rheological studies in academic and ...
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We present a comprehensive overview of microrheology, emphasizing the underlying theory, practical aspects of its implementation, and current applications to rheological studies in academic and industrial laboratories. Key methods and techniques are examined, including important considerations to be made with respect to the materials most amenable to microrheological characterization and pitfalls to avoid in measurements and analysis. The fundamental principles of all microrheology experiments are presented, including the nature of colloidal probes and their movement in fluids, soft solids, and viscoelastic materials. Microrheology is divided into two general areas, depending on whether the probe is driven into motion by thermal forces (passive), or by an external force (active). We present the theory and practice of passive microrheology, including an in-depth examination of the Generalized Stokes-Einstein Relation (GSER). We carefully treat the assumptions that must be made for these techniques to work, and what happens when the underlying assumptions are violated. Experimental methods covered in detail include particle tracking microrheology, tracer particle microrheology using dynamic light scattering and diffusing wave spectroscopy, and laser tracking microrheology. Second, we discuss the theory and practice of active microrheology, focusing specifically on the potential and limitations of extending microrheology to measurements of non-linear rheological properties, like yielding and shear-thinning. Practical aspects of magnetic and optical tweezer measurements are preseted. Finally, we highlight important applications of microrheology, including measurements of gelation, degradation, high-throughput rheology, protein solution viscosities, and polymer dynamics.Less

Microrheology

Eric M. FurstTodd M. Squires

Published in print: 2017-10-05

We present a comprehensive overview of microrheology, emphasizing the underlying theory, practical aspects of its implementation, and current applications to rheological studies in academic and industrial laboratories. Key methods and techniques are examined, including important considerations to be made with respect to the materials most amenable to microrheological characterization and pitfalls to avoid in measurements and analysis. The fundamental principles of all microrheology experiments are presented, including the nature of colloidal probes and their movement in fluids, soft solids, and viscoelastic materials. Microrheology is divided into two general areas, depending on whether the probe is driven into motion by thermal forces (passive), or by an external force (active). We present the theory and practice of passive microrheology, including an in-depth examination of the Generalized Stokes-Einstein Relation (GSER). We carefully treat the assumptions that must be made for these techniques to work, and what happens when the underlying assumptions are violated. Experimental methods covered in detail include particle tracking microrheology, tracer particle microrheology using dynamic light scattering and diffusing wave spectroscopy, and laser tracking microrheology. Second, we discuss the theory and practice of active microrheology, focusing specifically on the potential and limitations of extending microrheology to measurements of non-linear rheological properties, like yielding and shear-thinning. Practical aspects of magnetic and optical tweezer measurements are preseted. Finally, we highlight important applications of microrheology, including measurements of gelation, degradation, high-throughput rheology, protein solution viscosities, and polymer dynamics.

This chapter describes the properties arising due to the defining feature of polymers—the enormous size of their constituent molecules. This size and the large aspect ratio of ‘macromolecules’ cause ...
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This chapter describes the properties arising due to the defining feature of polymers—the enormous size of their constituent molecules. This size and the large aspect ratio of ‘macromolecules’ cause high elasticity and viscoelasticity. High elasticity refers to the ability of flexible-chain polymers to recover from large strains, a property unique to rubber. Viscoelasticity describes a time-varying reaction to a transient perturbation, unaccompanied by any change in the material; viscoelastic materials both dissipate and store energy during deformation. These two characteristics underlie most applications of rubbery materials. The chapter provides an overview of the molecular basis for the behavior, including the local and segmental motions, the chain dynamics, the effect of entanglements, and the application of fluctuation-dissipation theory.Less

Introduction

C. M. Roland

Published in print: 2011-06-30

This chapter describes the properties arising due to the defining feature of polymers—the enormous size of their constituent molecules. This size and the large aspect ratio of ‘macromolecules’ cause high elasticity and viscoelasticity. High elasticity refers to the ability of flexible-chain polymers to recover from large strains, a property unique to rubber. Viscoelasticity describes a time-varying reaction to a transient perturbation, unaccompanied by any change in the material; viscoelastic materials both dissipate and store energy during deformation. These two characteristics underlie most applications of rubbery materials. The chapter provides an overview of the molecular basis for the behavior, including the local and segmental motions, the chain dynamics, the effect of entanglements, and the application of fluctuation-dissipation theory.

The flow and deformation behaviours of soft matter are usually between those of fluids and elastic materials. For example, bubblegum can be stretched indefinitely like a fluid, but snaps back like an ...
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The flow and deformation behaviours of soft matter are usually between those of fluids and elastic materials. For example, bubblegum can be stretched indefinitely like a fluid, but snaps back like an elastic material if a stretched piece is cut by scissors. The science that studies the flow and deformation of such complex materials is called rheology. Rheology is important in soft matter since many applications of soft matter rely on their unique rheological properties. This chapter discusses the rheological properties of polymeric materials (polymer solutions, melts, and cross-linked polymers). It covers the methods of macroscopic characterization of rheological properties of materials; and the molecular origins of the unique rheological properties of polymeric materials for polymer solutions, polymer melts, and liquid crystalline polymers.Less

Flow and deformation of soft matter

Masao Doi

Published in print: 2013-06-04

The flow and deformation behaviours of soft matter are usually between those of fluids and elastic materials. For example, bubblegum can be stretched indefinitely like a fluid, but snaps back like an elastic material if a stretched piece is cut by scissors. The science that studies the flow and deformation of such complex materials is called rheology. Rheology is important in soft matter since many applications of soft matter rely on their unique rheological properties. This chapter discusses the rheological properties of polymeric materials (polymer solutions, melts, and cross-linked polymers). It covers the methods of macroscopic characterization of rheological properties of materials; and the molecular origins of the unique rheological properties of polymeric materials for polymer solutions, polymer melts, and liquid crystalline polymers.

General concepts of rheology and microrheology are presented, including basic concepts of the microrheology measurement, the characteristics of soft materials, rheological functions and principles of ...
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General concepts of rheology and microrheology are presented, including basic concepts of the microrheology measurement, the characteristics of soft materials, rheological functions and principles of conventional rheometric measurements, as well as several common rheological properties that will be encountered throughout the text. Microrheology encompasses a set of rheometric methods or techniques with unique capabilities|a part of the experimental toolbox for characterizing the rheological properties of materials to aid their understanding, or help in the design of new materials. There are limitations to microrheology that are important to understand from the outset. Colloidal particles are central to all microrheology measurements. Basic concepts of colloid science, including typical probe chemistries, colloidal stability, characterization, and preparation are presented.Less

Introduction

Eric M. FurstTodd M. Squires

Published in print: 2017-10-05

General concepts of rheology and microrheology are presented, including basic concepts of the microrheology measurement, the characteristics of soft materials, rheological functions and principles of conventional rheometric measurements, as well as several common rheological properties that will be encountered throughout the text. Microrheology encompasses a set of rheometric methods or techniques with unique capabilities|a part of the experimental toolbox for characterizing the rheological properties of materials to aid their understanding, or help in the design of new materials. There are limitations to microrheology that are important to understand from the outset. Colloidal particles are central to all microrheology measurements. Basic concepts of colloid science, including typical probe chemistries, colloidal stability, characterization, and preparation are presented.

The movement of colloidal particles in simple and complex fluids and viscoelastic solids is central to the microrheology endeavor. All microrheology experiments measure the resistance of a probe ...
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The movement of colloidal particles in simple and complex fluids and viscoelastic solids is central to the microrheology endeavor. All microrheology experiments measure the resistance of a probe particle forced to move within a material, whether that probe is forced externally or simply allowed to fluctuate thermally. This chapter lays a foundation of the fundamental mechanics of micrometer-dimension particles in fluids and soft solids. In an active microrheology experiment, a colloid of radius a is driven externally with a specifed force F (e.g.magnetic, optical, or gravitational), and moves with a velocity V that is measured. Of particular importance is the role of the Correspondence Principle, but other key concepts, including mobility and resistance, hydrodynamic interactions, and both fluid and particle inertia, are discussed. In passive microrheology experiments, on the other hand, the position of a thermally-uctuating probe is tracked and analyzed to determine its diffusivity.Less

Particle motion

Eric M. FurstTodd M. Squires

Published in print: 2017-10-05

The movement of colloidal particles in simple and complex fluids and viscoelastic solids is central to the microrheology endeavor. All microrheology experiments measure the resistance of a probe particle forced to move within a material, whether that probe is forced externally or simply allowed to fluctuate thermally. This chapter lays a foundation of the fundamental mechanics of micrometer-dimension particles in fluids and soft solids. In an active microrheology experiment, a colloid of radius a is driven externally with a specifed force F (e.g.magnetic, optical, or gravitational), and moves with a velocity V that is measured. Of particular importance is the role of the Correspondence Principle, but other key concepts, including mobility and resistance, hydrodynamic interactions, and both fluid and particle inertia, are discussed. In passive microrheology experiments, on the other hand, the position of a thermally-uctuating probe is tracked and analyzed to determine its diffusivity.

The wide number of microrheology methods and techniques serve as new tools for measuring the rheology of soft materials. Several emerging applications of microrheology are presented, including the ...
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The wide number of microrheology methods and techniques serve as new tools for measuring the rheology of soft materials. Several emerging applications of microrheology are presented, including the rheology of hydrogelators, gelation kinetics, and degradation (gel breaking). Viscosity measurements, in particular of protein solutions, is also discussed. These problems generally take advantage of the small volume requirements of microrheology as well as its sensitivity. The chapter begins with a discussion of mechanical and microrheology operating regimes to aid the reader in planning experiments. It concludes with a discussion of emerging trends and future areas of microrheology, including interfacial rheology.Less

Microrheology applications

Eric M. FurstTodd M. Squires

Published in print: 2017-10-05

The wide number of microrheology methods and techniques serve as new tools for measuring the rheology of soft materials. Several emerging applications of microrheology are presented, including the rheology of hydrogelators, gelation kinetics, and degradation (gel breaking). Viscosity measurements, in particular of protein solutions, is also discussed. These problems generally take advantage of the small volume requirements of microrheology as well as its sensitivity. The chapter begins with a discussion of mechanical and microrheology operating regimes to aid the reader in planning experiments. It concludes with a discussion of emerging trends and future areas of microrheology, including interfacial rheology.